BRPI0706982A2 - solid phase polymerization catalyst to generate low acetaldehyde polyester resins - Google Patents

Abstract

This invention discloses a process for producing a polyester resin having a low acetaldehyde generation rate comprised of the steps of polycondensing the polyester resin in the presence of tin and antimony; wherein the tin is present within the range of 50 to 110 ppm of the polyester resin and the antimony is present from 105 ppm to 265 ppm of the polyester resin, and solid phase polymerizing the polyester resin for sufficient time so as to increase the intrinsic viscosity of the polyester resin by at least 0.15 dl/g.

Description

Solid phase polymerization catalyst for generating polyester resins under acetaldehyde.

The present invention relates to the field of manufacturing polyester resins using a solid phase polymerization process to more rapidly condense polyester resin while still producing a polyester resin with a low acetaldehyde generation rate.

Polyester resins used in packaging have unique requirements. They are usually manufactured to make a low molecular weight polymer in the liquid phase, pellet the polymer and then subject those pellets to solid phase polymerization to further increase the molecular weight. It is well known in the art that some catalysts (eg titanium) work very well in the liquid or melt polymerization step, but do not catalyze sandblasting in the solid phase step.

The choice of catalyst is also important because it is also known that different catalysts will affect the amount of acetaldehyde generated when the polyester resin is melted and injection molded into a preform cast into a sheet. Minimization of acetaldehyde is a particular objective for packaging used to contain water. Acetaldehyde is absorbed by water from the packaging, negatively affecting the taste of water.

There is therefore a need for a catalyst or catalyst system that provides acceptable rates of gas phase polymerization and yet forms a reduced amount of acetaldehyde.

The combination of tin and antimony has been found to provide such a catalytic system.

The use of catalytic combinations of antimony and tin is well known in the ancient polyester technique. JP 54-135896, published October 22, 1979, describes the use of antimony, tin, cobalt and a polycondensation alkali metal in molten melt to produce a good color film resin.

JP 54-135896 describes nothing about the ability of the catalyst to function as a gas phase polymerization catalyst or the role of the catalyst in reducing the amount of acetaldehyde generated during subsequent melt processing.

JP 52-123489, published October 17, 1977, describes the use of antimony and tin during fused polycondensation catalysis to produce a good colored film resin. JP 52-123489 describes the ability of the catalyst to function as a gas phase polymerization catalyst or the role of the catalyst in reducing the amount of acetaldehyde generated during subsequent melt processing. JP 53-052595, issued May 13 1978, describes the use of antimony and tin during fused polycondensation catalysis to produce a good color film resin. JP 53-052595 is described in regard to the ability of the catalyst to function as a gas phase polymerization catalyst or the role of the catalyst in reducing the amount of acetaldehyde generated during subsequent melt processing.

GB 1236949, published June 23, 1971, describes the use of antimony and tin as a catalyst for melt polyester condensation for use in fibers. GB 1236949 discloses nothing about the ability of the catalyst to function as a fasegasas polymerization catalyst or the role of the catalyst in reducing the amount of acetaldehyde generated during subsequent melt processing.

US 5,714,570 describes the use of antimony, tin in combination with titanium, as a melt polycondensation catalyst. US 5,714,570 discloses nothing about the ability of the catalyst to function as a gas phase polymerization catalyst or the role of the catalyst in reducing the amount of acetaldehyde generated during subsequent melt processing.

The present invention describes a process for producing a polyester resin having a low acetaldehyde generation rate comprising polycondensing the polyester resin in the presence of tin and antimony; wherein the tin is present within the range of 50 to 110 ppm of the polyester resin and the antimony is present of 105 to 265 ppm of the polyester resin, and solid phase polymerization of the polyester resin occurs long enough to increase intrinsic viscosity of the resin. of polyester at least 0.15 dL / g.

Further disclosed is a catalytic composition for producing a low-generation acetaldehyde polyester resin using a solid state process, wherein said catalytic composition comprises tin and antimony; wherein the tin is present within the range of 50 to 110 ppm of the polyester resin and the antimony is present of 105 to 265 ppm of the polyester resin.

It is further described that the catalyst additionally comprises an equivalent molar amount of cobalt and phosphorus, wherein cobalt is present in at least 15 ppm of the polyester resin.

The present invention is based on the discovery that antimony-tin combining can be used in the solid phase polymerization process, and yet at the same time exhibits reduced catalytic activity for acetaldehyde formation when the polyester resin is subsequently processed. This allows to take advantage of the fast melt polymerization of the antimony-tin combination while obtaining a low acetaldehyde generation rate.

Although virtually any non-elemental antimony compound works, preferred antimony compounds used as catalysts for preparing polyesters include antimony oxides such as antimony trioxide, antimony tetraoxide or antimony pentoxide, antimony halides such as antimony trichloride or antimony trifluoride , antimony carboxylates, such as antimony triacetate, antimony triestearate, antimony tribenzoate, antimony triethylhexanoate or antimony trioctoate, an antimony combined with ether, such as antimony trimethoxide, antimony ethylene oxide, triisopropoxide, antimony tri-n-butoxide and antimony triphenoxide, antimony hydroxide and antimony sulfides. Of these compounds, deantimonium trioxide and antimony triacetate are particularly preferred.

As with antimony, virtually any non-elemental tin compound will work. Preferred organotin catalysts for use in the present invention all include at least one direct carbon-tin bond and one direct oxygen-tin bond. They can be described by the general formula.

<formula> formula see original document page 4 </formula>

on what

R may be the same or different when more than one R is present,

R is an alkyl of 1 to about 20 carbon atoms, or an aryl, alkylaryl or cycloalkyl of 6 to about 14 carbon atoms, and R may be saturated or unsaturated, substituted or unsubstituted; and

m may be 1 or 2, provided that when m = 1, (OX) represents O1, 5, (O) OH or (OR1) 3; equating m = 2, (OX) represents O or (OR1) 2;

wherein R1 may be the same or different when more than one R 'is present, R1 is hydrogen, an alkyl of 1 to about 20 carbon atoms, or the residue of a mono- or multifunctional alcohol, carboxylic acid or ester;

provided that when R1 is the residue of a multifunctional alcohol, carboxylic acid, or ester, including one having two or more hydroxyl groups, two or more carboxylic acid groups, or one each, then the organotin compound may contain two or more organo-tin moieties in the same molecule bonded together through the residue of the multifunctional anion, so that in each instance where a multifunctional anion is bonded to two or more tin atoms, the organo-tin catalyst may be a dimer, trimer or polymer of higher molecular weight; and furthermore, when (OX) represents (OR1) 2 or (OR1) 3, one or two of the (OR1) 1 groups respectively may be replaced by an anion bonded to tin through a non-oxygen atom such as sulfur, phosphorus or nitrogen, or a monovalent ion, such as a halide bonded directly to tin.

The triorgane-tin content of the present catalysts should preferably be less than about 5%. Compostostriorgane-tin (i.e., m = 3 in the above formula) do not fall within the scope of the above formula, but are often undesirable by-products in the manufacture of other organo-tin compounds. Because triorgane-tin compounds are generally considered toxic, their content in catalysts should be minimized. Heavy metals are also undesirable impurities, and therefore the nocatalyst heavy metal content is preferably less than 200 parts per million (ppm).

The organotin catalysts of the present invention may comprise one or more organotin compounds according to the above formula. However, each component of the organotin compound should preferably be at least 90% pure.

Examples of the present invention organotin catalysts exemplified by the generic formula RmSn (OX) include those of the following Table I:

TABLE 1 - Examples of Tin Compounds

<table> table see original document page 5 </column> </row> <table> <table> table see original document page 6 </column> </row> <table>

Preferred organotin catalysts include, but are not limited to, hydroxybutyl tin oxide (also known as butyl stannic acid), monobutyl tin tris (2-ethylhexoate), and dibutyl tin oxide.

Other non-organic tin, such as tin oxide, are likewise included.

The amount of tin present may be in the range of 30 to 120 parts per million polyester resin, with 35 to 110 parts and 50 to 100 parts per million polyester resin being the most suitable amounts of tin.

The amount of antimony present may range from about 95 to 300 parts per million of polyester resin, with 105 to 285 and 105 to 265 parts per million of polyester resin being more suitable.

Suitable polyesters for the present invention are those polyesters which are capable of being solid phase polymerized. Polyester polymers and copolymers may be prepared by melt polymerization involving the reaction of a diol with a carboxylic acid or its corresponding diester. Various copolymers resulting from the use of multiple diols and diacids may also be used. Polymers containing repeating units of a single chemical composition are homopolymers. Polymers with two or more chemically different repeating units in the same macromolecule are called polymers. For the sake of clarity, a terephthalate, isophthalate and naphthalate cometylene glycol, diethylene glycol and cyclohexanedimethanol polymer contain six distinct monomers and is considered a copolymer. The diversity of repeating units depends on the number of different types of monomers present in the initial polymerization reaction. In the case of polyesters, copolymers include reacting one or more diols with one or more diacids, and are sometimes called terpolymers. Additionally, randomization of monomers is not required. A copolymer or terpolymer also refers to a polymer with different monomers, whether in block distribution or statistically.

Suitable dicarboxylic acids include those comprising from about 6 to about 40 carbon atoms. Specific dicarboxylic acids include, but are not limited to, terephthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid, cyclohexanedicarboxylic acid, cyclohexanediacetic acid, diphenyl-4,4'-dicarboxylic acid, 1,3-phenylenedioxyacetic acid, 2-phenylenedioxyacetic acid, 1,4-phenylenedioxyacetic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and the like. Specific esters include, but are not limited to, phthalic esters and naphthalic diesters.

Also included are monomers that create polyester ionomers such as metallosulfonates. These include lithium, sulfur and phosphorus isophthalate sulfonate salts.

These acids or esters may be reacted with a diolaliphatic having from about 2 to about 10 carbon atoms, a cycloaliphatic diol having from about 7 to about 14 carbon atoms, an aromatic diol having from about 6 to about 15 atoms. or a glycol ether having from 4 to 10 carbon atoms. Suitable diols include, but are not limited to, 1,4-butanediol, trimethylene glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, diethylene glycol, resorcinol and hydroquinone.

Polyfunctional comonomers may also be used, typically in amounts of from about 0.1 to about 3 mole%. Suitable comonomers include, but are not limited to, trimellitic anhydride, trimethylpropane, pyromellitic dianhydrid (PMDA) and pentaerythritol. Polyester or polyester forming polyols may also be used.

A preferred polyester is poly (ethylene terephthalate) (PET homopolymer) formed from the approximately 1: 1 stoichiometric reaction of terephthalic acid or its ester with ethylene glycol. Another preferred polyester is opoly (ethylene naphthalate) (PEN homopolymer) formed from the approximately 1: 1 to 1: 1.6 stoichiometric reaction of naphthalene dicarboxylic acid, or ester thereof, with ethylene glycol. Yet another preferred polyester is poly (butylene terephthalate) (PBT). PET1 copolymers PEN copolymers and PBT copolymers are also preferred. Specific copolymers and terpolymers of interest are PET in combinations of isophthalic acid or its diester, 2,6-naphthalic acid or its diester, and / or cyclohexanedimethanol.

Another preferred polyester is poly (detrimethylene terephthalate). It can be prepared, for example, by reacting 1,3-propanediol with at least one aromatic diacid or its alkyl ester. Preferred alkyl diacids and esters include terephthalic acid or dimethyl terephthalate (DMT). Accordingly, PTT preferably comprises at least about 80 mole% TPA or DMT. Other diols that can be copolymerized to such a polyester include, for example, ethylene glycol, diethylene glycol, 1,4-cyclohexanedimethanol and 1,4-butanediol. Aliphatic aromatic acids that can be used simultaneously to make a copolymer include, for example, isophthalic acid and sebacic acid.

The polyester melt fabrication step usually takes place in two steps, the first step is the reaction of the raw materials to form low molecular weight polygomers. This step is typically called the esterification step. In the ester process, it is known as the transesterification step. The low molecular weight polymers are then subjected to a condensation step. It has been found that it is preferred to add the catalytic composition of the present invention after the esterification step, just prior to the postcondensation step, to avoid the need for additional polycondensation catalyst.

After the melt polymerization phase is completed, the liquid polymer is cooled and then formed into pellets or chips. The polyester cavities are crystallized and then solid phase polymerized (SSP) to increase the molecular weight as measured by the intrinsic viscosity required for bottle making. Crystallization and polymerization may be performed in a tumbling drier reaction in a batch type system. Alternatively, crystallization and polymerization may be carried out in a continuous solid phase process wherein the polymer flows from one container to another after its predetermined heat treatment in each container.

Crystallization conditions for polyester preferably include a temperature from about 100 ° C to about 150 ° C.

Solid phase polymerization conditions preferably include a temperature of from about 200 ° C to about 235 ° C, and more preferably from about 215 ° C to about 235 ° C, and include a nitrogen sweep or vacuum to remove the particles. by-products of increased pesomolecular. Solid phase polymerization may be performed long enough to raise the molecular weight to the desired level, which will depend upon the application and initial intrinsic viscosity. For a typical bottle application, the preferred molecular weight corresponds to an intrinsic viscosity of about 0.68 to about 0.88dL / g as determined by the methods described in the methods section. The time required to achieve this molecular weight may range from about 8 to about 45 hours. Typical increases in I.V. are at least 0.1 dL / g, with increases from 0.2 to 0.4 dL / g being more typical.

Working Example 1

7607 g terephthalic acid, 235 g isophthalic acid, 0.0117 g SB138 dye, 0.0023 g SV50 dye were loaded into a container containing a "hop" of approximately X g of low molecular weight oligomers of the same final composition. The charged contents and the jump were mixed at atmospheric pressure for 10 minutes and 267 ° C.

After ten minutes, 3106 g of sufficient ethylene glycol, sodium acetate and H 3 PO 4 were added to achieve 0.001 ppt Na and 0.013 ppt phosphorous based on the final amount of polymer. The contents were then stirred at 275 - 278 ° C, 3,378 bar until 1500 mL of water had evolved (3h, 11min).

Approximately 1/3 of the contents of the container were then transferred to a second container for polycondensation. The remaining content in the first container will "jump" to the next fresh batch to be loaded.

The contents of the second container were then polycondensed after adding 0.012 ppt of cobalt, based on the final polymer as cobalt acetate, and mixed for 3 minutes, 0.130 ppt of antimony, based on the final polymer such as antimony oxide, and mixed for 3 minutes. , and 0.080 ppt demonobutyl tris (2-ethylhexoate), based on the final polymer, 0.907 g FeP (iron phosphide) and 150 g ethylene glycol. Polycondensation was performed by mixing the vessel at 272 ° C and reducing the pressure from 720 torr (95.992 Pa) to 1 torr (133 Pa) over a period of 1 hour. After reaching 1.0 torr (133 Pa), the pressure was reduced to 0.1 torr (13.3 Pa) and then the polymer was polycondensed until a pre-set torque was reached on a constant rpm stirrer. In this example, it was 26 minutes. This final step is apollondensation reported in Table I. The final polymer was then discharged into epellised yarns.

The properties of the polymer were intrinsic viscosity of 0.457 dL / g, 52 meq carboxyl, melting point 247 ° C, L * = 53.06, a * = -0.91 and the fused polycondensate polymer was then polymerized to solid phase in a rotary vacuum solid state reactor. Several batches of fused resin were combined in a large rotating vacuum vessel and exposed to the crystallization step followed by the actual polymerization step. Crystallization was performed by lowering the pressure to 0.1 torr and adjusting the hot oil temperature to 120 ° C for 3 hours. After the resin had crystallized, the oil temperature was increased to 230 ° C and the polymer was stirred in the rotating vessel until final IV was reached. Samples were taken every 2 hours and analyzed for IV. be determined by the change in IV per unit of time. In this particular example, the material was prematurely cooled to 0.719 dL / g and then reheated 2 hours to final I.V. of 0.745 dL / g.

The solid phase polymerization rate for the uninterrupted cycle ending at 0.719 dL / g from 0.452 dL / g occurred for 12 hours or 0.02225 dL / g / h.

The rate of acetaldehyde generation was determined by taking the finished polymer and injecting it into preforms at the same temperature but at different cycle times. The preforms were then analyzed for acetaldehyde that was formed during the injection cycle. From this information the rate of acetaldehyde generation can be determined. One skilled in the art will also recognize that one could vary the temperature and determine the kinetics as well. The acetaldehyde generation rate of this polymer was 1.81 ppm / min.

Comparative Examples

Several comparative examples have been performed by varying antimony and tin levels. Your data along with the sample work are presented in Table II - Results.

<table> table see original document page 10 </column> </row> <table>

In the following set of experiments, shown in Table III, the results were validated on a larger portion of the continuous polyester fabrication line. These exhibit very similar AAGR (AA generation rates with an increased polycondensation productivity of 7.5% for the claimed catalytic combination. While 7.5% improvement may seem little, in large installations operating at 15 tons per hour means the installation is capable of producing over 1,125 tons per hour, or approximately 8,800 tons per year.

TABLE III - Results of continuous tests

<table> table see original document page 11 </column> </row> <table>

Methods

The intrinsic viscosity of low molecular weight intermediate molecular weight poly (ethylene terephthalate) and related polymers which are soluble in 60/40 phenol / tetrachloroethane can be determined by dissolving 0.1 g of the ground polymer or pellet in 25 mL of 60/40 phenol. / tetrachloroethane and determining solution viscosity at 30 ° C ± 0.05 with respect to the solvent at the same temperature using a Ubbelohde 1B viscometer. Intrinsic viscosity is calculated using the Billmeyer equation based on relative viscosity.

The intrinsic viscosity of highly crystalline high molecular weight poly (ethylene terephthalate) and relative polymers that are not soluble in phenol / tetrachloroethane was determined by dissolving 0.1 g of the polymer or pelletemoide in 25 ml of 50/50 trifluoroacetic acid / dichloromethane and determining solution viscosity at 30 ° C ± 0.05 with respect to the solvent at the same temperature using a Ubbelohde Type OC viscometer. Intrinsic viscosity is calculated using the Billmeyer equation and converted using a linear regression to obtain results that are consistent with those obtained using 60/40 phenol / tetrachloroethane solvent. Linear regression is

I-V.60 / 40 phenol / tetrachloroethane = 0.8229 X I.V.50 / 50 trifluoroacetic acid / dichloromethane + 0.0124.

Claims (2)

1. "Process for producing a polyester resin with a low acetaldehyde generation rate", characterized in that it comprises the steps of: - polycondensing the polyester resin in the presence of tin and antimony; wherein the tin is present within the range of 30 to 110 ppm of the polyester resin and the antimony is present of 95 to 300 ppm of the polyester resin, and solid-phase polymerize the polyester resin long enough to increase the intrinsic viscosity of the resin. of polyester at least 0.15 dL / g. 2. "Catalytic composition", to produce a low-generation acetaldehyde depolyester resin using a solid state process, characterized in that said catalytic composition comprises tin and antimony, wherein tin is present within the range of 30 to 110 ppm. of polyester resin and antimony are present from 95 to 300 ppm of polyester resin; and wherein the catalyst additionally comprises a molar equivalent amount of cobalt and phosphorus, wherein cobalt is present in less than 15 ppm of the polyester resin.